A bus moving at a speed of 45 km/hr catches a truck 150 metres ahead going in the same direction in 30 seconds. The speed of the truck is :

Solution(By Examveda Team)

Let the speed of truck is = x km/hr
Their relative speed in same direction = (45 - x) km/hr
[Here (45 - x) has been written because bus crosses the truck which is running 150 metres ahead of it. i.e., Truck speed will be lower than that of bus]
According to the question,
$$\eqalign{ & {\text{Time}} = \frac{{{\text{Distance}}}}{{{\text{Speed}}}} \cr & \Rightarrow \frac{{150}}{{\left( {45 - x} \right) \times \frac{5}{{18}}}} = 30 \cr & \Rightarrow \frac{{150 \times 18}}{{\left( {45 - x} \right) \times 5}} = 30 \cr & \Rightarrow x = 27{\text{ km/hr}} \cr} $$